Valve for metered admixing of volatilized fuel to the fuel/air mixture of an internal combustion engine

ABSTRACT

A tank vent valve for the metered admixing of volatilized fuel to the fuel/air mixture of an internal combustion engine has a valve housing with inflow and outflow sockets, between which is arranged an electromagnetically operable seated valve, which is spring loaded in the closing direction by a valve closing spring. For the simple design of the tank valve, the valve opening of the seat is arranged as a ring gap nozzle in the return yoke of the electromagnet, and the valve double seat which acts in conjunction with the valve member and which surrounds the ring gap nozzle is arranged on that side of the return yoke which faces the inflow socket. For setting the stroke of the valve member, the hollow cylindrical magnet core of the magnet housing can be threaded by means of an adjusting thread in the magnet housing. Supported on the magnet core is a valve closing spring, which loads the valve member which is formed by the armature of the electromagnet, in the closing direction.

STATE OF TECHNOLOGY

The invention concerns a valve for the metered admixing of fuel whichhas volatilized from the fuel tank of an internal combustion engine, tothe fuel/air mixture, which is fed to the internal combustion engine viaan inlet manifold.

Based on the statutory requirements in some countries for the protectionof the environment, the fuel which volatilizes in a fuel tank, known asthe petrol vapour, must not be vented to the atmosphere, but must beburned within the internal combustion engine. For this purpose, the ventsocket of the fuel tank is connected to a reservoir filled withactivated carbon, which takes in the volatilized fuel when the internalcombustion engine is stationary, and discharges it again when the engineis running. For this purpose, the reservoir is connected to the internalcombustion engine via a suction line from the induction manifold, wherethe fuel vapour is admixed to the fuel/air mixture. The possibleincrease in exhaust gas emission resulting from this, requires admixingof the fuel vapour only in certain operating conditions of the internalcombustion engine and in certain quantities. This is effected by thetank vent valve mentioned earlier, which is arranged in the inductionmanifold between the reservoir and the suction pipe and which is openedand closed by electronic control, preferably timed, depending on theoperating condition of the internal combustion engine and the exhaustgas emission, which is measured with a lambda probe. In order to preventrunning-on after switching off the engine, the seated valve which isintegrated in the tank vent valve is designed currentless. The dualfunction of the annular valve member, which at the same time forms thearmature of the electromagnet, facilitates a low movable armature massand hence brief switching periods of the seated valve.

With such tank vent valves, it is desirable to adapt the stroke of thevalve member on the pressure difference between the pressures upstreamand downstream of the valve seat in such a way that the stroke is smallduring off-load running of the engine (large pressure difference) andthat it becomes increasingly larger as the engine load increases(reducing pressure difference).

With such a stroke adaptation and the thus effected change of thecyclically opened cross-section of flow, greater accuracy is achieved inthe control of small throughput quantities with a large pressuredifference on the valve seat (off-load running) which does not requireextremely small switching times, such as would be required with aconstant valve stroke for the control of these small throughputquantities. The electromagnet can thus be built small and of lightweight.

In a known tank vent valve of the type mentioned earlier (DE 38 44 453Al), such a stroke adaptation is implemented by the valve double seatwith the valve opening being configured on an intermediate ring which isclamped in a housing, and also by that side of the intermediate ringwhich faces the inflow socket, having a bellows attached by one of itsfront faces, the other front face being fixed to the bottom of a potwhich embraces the bellows with radial separation. The rim of the potchanges into an annular collar which protrudes radially beyond theannular valve opening, this collar having a number of axial holes whichare distributed in a circumferential direction and which are aligned inan axial direction with the valve opening. On its side which faces thepot, the intermediate ring has a sealing seat which surrounds the valveopening on the inside and the outside, and which acts together with theannular collar of the pot which functions as a closing member. If thevacuum pressure increases on the inflow socket, then the bellowscontract. The annular collar approaches the sealing seat, and the flowcross-section at the sealing seat is reduced. The limit is reached whenthe annular collar of the pot rests on the sealing seat. The axial holesin the annular collar then determine the remaining opening cross-sectionof the seat valve.

Such a design arrangement of the tank vent valve is very elaborate inits construction and therefore requires relatively high manufacturingcosts.

ADVANTAGES OF THE INVENTION

The tank vent valve in accordance with the invention, has the advantageof creating a seated valve, at low manufacturing costs, which is closedfree from potential, with a valve member stroke which is largelygoverned by the pressure difference upstream and downstream of the valveseat. Due to the jet action of the ring gap nozzle, increasing negativepressure in the suction pipe of the engine, and hence on the outflowsocket of the tank vent valve, causes the valve member and the armatureto be more strongly drawn into the direction of the valve double seat.This suction force acts in opposition to the force of the electromagnet.The integration of the ring gap nozzle in the return yoke eliminates theneed for a separate valve seat support, and the valve becomes lessexpensive to manufacture. Because of the suction effect of the ring gapnozzle, the valve closing spring, which acts in the suction direction,can be made very much smaller. The screwed connection between the magnetcore and the magnet housing facilitates a simple axial displacement ofthe magnet core and thus a very simple setting of the stroke stop forthe armature.

In accordance with a preferred embodiment of the invention, the ring gapnozzle is arranged in the base of a cavity in the return yoke, and thevalve member or the armature is arranged axially displaceable, with asmall radial separation in the cavity, by means of a leaf spring held inthe valve housing, preferably made of non-magnetic material. Thisensures a simple guidance of the armature. The leaf spring is of suchtolerance that any lateral magnetic tilting of the armature isprevented.

The volatilized fuel, which flows from the inflow socket via the seatedvalve to the outflow socket, in accordance with a further embodiment ofthe invention, is passed through both the hollow cylindrical magnet coreand through axial channels between the magnet housing and the valvehousing. This allows efficient dissipation of the heat generated in thecyclic operation of the electromagnet.

When the tank vent valve is used in supercharged engines, a non-returnvalve is required, which opens towards the outflow socket. In accordancewith a further embodiment of the invention, such a non-return valve isintegrated in the valve housing in a simple manner, between the valveseat and the outflow socket. The valve seat of the non-return valve isarranged on the valve housing, and its valve member is pressed onto thevalve seat with a valve spring which is supported on the outflow socket.Drawing

The invention is described in more detail below and by means of anembodiment example represented in the drawing. The drawing shows:

FIG. 1 a longitudinal section of a tank vent valve,

FIG. 2 a longitudinal section of a return yoke of an electromagnet inthe tank vent valve according to FIG. 1,

FIG. 3 a top view of the return yoke of FIG. 2.

DESCRIPTION OF THE EMBODIMENT EXAMPLE

The valve, shown schematically in longitudinal section in FIG. 1, forthe metered admixing of fuel which has volatilized from the fuel tank ofan internal combustion engine, via a suction pipe, to the fuel/airmixture, hereafter referred to as the tank vent valve, is used in anoutput unit for the introduction of volatilized fuel into an internalcombustion engine, such as the one described in the DE 35 19 292 A1. Thetank vent valve has a two-part valve housing 10 with a pot shapedhousing part 101 and a cap-like housing part 102 which closes thehousing part 101. The housing part 101 supports an inflow socket 11 forthe connection to a vent socket of the fuel tank or to a reservoir,downstream from it, which is filled with activated carbon for thevolatilized fuel, while the housing part 102 supports an outflow socket12 for the connection to the induction manifold of the internalcombustion engine. The inflow socket 11 and the outflow socket 12 arearranged axially in the housing parts 101 and 102. Arranged inside thepot-shaped housing part 101 is an electromagnet 13. It has a pot-shapedmagnet housing 14 with a coaxial, hollow cylindrical magnet core 15which penetrates the pot bottom, and a cylindrical field coil 16 whichis seated on a coil support 17 and which rests in the magnet housing 14,embracing the magnet core 15. Arranged at the bottom of the magnethousing 14 in one piece is an outwardly projecting threaded neck 18 withan internal thread 19, within which an externally threaded section 20 isthreaded on the hollow cylindrical magnet core 15. By turning thethreaded section 20, the magnet core 15 can be axially displaced in themagnet housing 14. The magnet core 15 rests flush with the inflow socket11, so that the volatilized fuel which flows in at this point passesdirectly into the magnet core 15 and flows through the magnet core. Themagnet housing 14 with the magnet core 15 is arranged in the pot-shapedhousing part 101 in such a way that axial channels remain between theouter casing of the magnet housing 14 and the inner casing of the valvehousing 10, which are circumferentially displaced by equal angles. Thelongitudinal section of FIG. 1 shows only the two diametrically opposedaxial channels 21,22. These channels 21,22 are linked, on the one hand,via an annular space 23 which remains between the valve housing 10 andthe externally threaded section 20 of the magnet core 15, with theinflow socket 11 and, on the other hand, via holes 24 which are providedin the magnet housing 14 near the open end of the magnet housing 14,with the interior of the magnet housing 14. The volatilized fuel whichemerges from the inflow socket 11 flows through these axial channels21,22 and also around the magnet housing 14 and dissipates the heatwhich develops there.

The edge of the magnet housing 14 is angled to the outside to form anannular support flange 25, which is bent at the end to form an axiallyprotruding annular link 26. The support flange 25 is used for locating areturn yoke 27 which covers the magnet housing 14 and rests on the edgeagainst the annular link 26. The return yoke 27 shown in section inFIGS. 2 and 3, and magnified in the plan view is positioned by twolocating holes 28, on two holding spigots 29 in the cap shaped housingpart 102, which project axially on the underside which faces the housingpart 101. On engagement of the cap-type housing part 102 in the pot-typehousing part 101, the return yoke 27 is accurately seated into thesupport flange 25 with the annular link 26 nad is firmly clamped in it.Between the support flange 25 and the return yoke 27, a leaf spring 30,made of nonmagnetic material such, as bronze, is clamped and centred onthe holding spigot 29 and supports the armature of the electromagnet 13.

The electromagnet 13 is used for the timed switching of a seated valve31, which is arranged between the inflow socket 11 and the outflowsocket 12. The seated valve 31 has a valve double seat 32 (FIG. 2),which is arranged at the base of a cavity 33 in the return yoke 27, onthat side which faces the inflow socket 11. The cavity 33 is designed sothat the base of the recess 33 which supports the valve double seat 32points to the magnet core 15. The valve double seat 32 coaxiallyembraces externally and internally a ring gap nozzle 34, which isconstructed as two symmetrical semi-circular arc gap 35,36 in the returnyoke 27. Acting in conjunction with the valve double seat 32 is a valvemember in the form of a ring disc 37 of magnetic material, which at thesame time forms the armature of the electromagnet 13. With a centeringarrangement 38, the ring disc 37 engages through a circular recess inthe leaf spring 30 and is fixed to this. The ring disc 37 is dimensionedso that its axial thickness is slightly less than the clearance diameterof the cavity 33, so that only an extremely small ring gap 40 remainsbetween the outer circumference of the ring disc 37 and the inner casingof the cavity 33. The leaf spring is toleranced such as to reliablyprevent any lateral magnetic tilting of the ring disc 37. The ring disc37 carries on its side which faces the valve double seat 32 a rubberseal 41. In the locking condition of the seated valve 31, the ring disc37 is pressed with its side which carries the rubber seal 41 onto thevalve double seat 32 by the action of a valve closing spring 49. Duringthis action, the valve closing spring 49 is, on the one hand, supportedon the ring disc 37 and, on the other hand, on an annular supportshoulder 50, which is arranged on the inner wall of the hollowcylindrical magnet core 15. The free face of the magnet core 15 forms astop 51 for the stroke movement of the ring disc 37. The adjustingthread, which is formed by the internal thread 19 and the externalthread section 20, allows the stop 51 to be displaced axially andthereby determining the quantity of flow with seat valve 31 opened toits maximum. The valve closing spring 49 is of small size, since asuction effect on the ring disc 37 is exerted in the direction of valveclosing when there is a pressure difference between the outflow socket12 and the inflow socket 11, this suction effect thus supporting theclosing action of the valve spring 49.

The rear of the return yoke 27 which faces away from the valve doubleseat 32 is sealed by a sealing ring 42 against the housing part 102, sothat any leakage losses via the connection of the return yoke 27 and themagnet housing 14 are avoided. The outflow socket 12 is engaged in anoutflow socket 12 which is designed coaxially on the housing part 102. Avalve seat 44 of a non-return valve 45 is arranged in the locatingsocket 43 on a radially inward projecting ring shoulder, and a valvebody 46 is pressed onto it by a valve spring 47. The valve spring 47 issupported on a shoulder 48 which is provided within a locating socket43. The non-return valve 45 is needed when the tank vent valve is to beused in supercharged engines.

The method of operation of the tank vent valve described above is asfollows:

When the electromagnet 13 is without current, the seated valve 31 isclosed, since the ring disc 37 with its rubber seal 41 is pressed ontothe valve double seat 32 by the valve closing spring 49. Duringoperation of the internal combustion engine, the electromagnet 13 iscontrolled by an electronic timing system. The timing frequency isconditioned by the operating condition of the internal combustionengine, so that the flow quantity of volatilized fuel flowing via theseat valve 31 from the inflow socket 11 into the outflow socket 12 ismetered accordingly. Superimposed on this electromagnetic control of theseated valve 31 is an influence exerted by the stroke of the ring disc37, which is due to the suction of the ring gap nozzle 34. The largerthe pressure difference between the outflow socket 12 and the inflowsocket 11, which reaches the maximum at no-load running of the engine,the larger is the suction action of the ring gap nozzle 34 and hence thesuction force which acts on the ring disc 37 in opposition to the forceof the electromagnet 13. As the load on the internal combustion engineincreases, the negative pressure of the outflow socket 12 reduces, andit becomes minimal at full load. The pressure difference between theinflow socket 11 and the outflow socket 12 is small, and so too is thesuction on the ring gap nozzle 34. With the electromagnet 13 beingenergized, the ring disc 37 performs its full stroke up to the stop 51.The flow quantity then passing through the aperture cross-section can beadjusted with high accuracy by rotatint the magnet core 15 in the threadadjustment 19,20.

The invention is not restricted to the embodiment example described.Instead of centering the leaf spring 30 on the housing part 102, thiscan be done on the return yoke 27 by means of spigots of the same type.

The foregoing relates to a preferred exemplary embodiment of theinvention, it being understood that other variants and embodimentsthereof are possible within the spirit and scope of the invention, thelatter being defined by the appended claims.

We claim:
 1. A valve for the metered admixing of fuel, which has volatilized from a fuel tank of an internal combustion engine, to a fuel/air mixture which is fed to the internal combustion engine via an induction manifold, a valve housing which has an inflow socket for a first connection to a vent socket of the fuel tank or to an activated carbon reservoir which is connected downstream from the fuel tank, for the volatilized fuel, an outflow socket for a second connection to an induction manifold, a seat valve, which is arranged inside the valve housing between said inflow and outflow sockets, a valve double seat surrounding an annular valve opening, an annular valve member which acts in conjunction with said valve double seat, said annular valve member being loaded by a valve closing spring in the direction of valve closing, and operable by an electromagnet in the direction of the valve opening, this electromagnet having a pot shaped magnet housing which is arranged coaxially relative to the valve opening, a hollow cylindrical magnet core arranged centrally in the magnet housing, a field coil which lies in the annular space between the magnet core and the magnet housing, a return yoke covering the magnet housing, and an armature which forms the valve member and which is of magnetically conductive material, the valve opening is arranged as a ring gap nozzle (34) in the return yoke (27) and that the valve double seat (32) is designed on the side of the return yoke (27) which faces the inflow socket (11), and that the hollow cylindrical magnet core (15) can be screwed into an adjusting thread (19, 20) provided in the base of the magnet housing (14) and carries a shoulder (50) for the valve closing spring (49) which is supported against the armature (37).
 2. A valve in accordance with claim 1, in which the ring gap nozzle (34) is arranged at a base of a cavity (33) in the return yoke (27) and that the armature (37) is axially slidable in the cavity (33) with a small radial separation.
 3. A valve in accordance with claim 2, in which the armature (37) is fixed to a leaf spring (30) which is clamped in the valve housing (10) and that the leaf spring (30) is toleranced so that any tilting of the armature (37) in the cavity (33) is reliably prevented.
 4. A valve in accordance with claim 3, in which the leaf spring (30) consists of a non-magnetic material such as copper and bronze, for example.
 5. A valve in accordance with claim 1, in which axial channels (21, 22) are provided between the magnet housing (14) and the valve housing (10), which are linked with the inflow socket (11) and with the interior of the magnet housing (14) via openings (24) arranged near the return yoke (27) in the magnet housing (14).
 6. A valve in accordance with claim 2, in which axial channels (21, 22) are provided between the magnet housing (14) and the valve housing (10), which are linked with the inflow socket (11) and with the interior of the magnet housing (14) via openings (24) arranged near the return yoke (27) in the magnet housing (14).
 7. A valve in accordance with claim 3, in which axial channels (21, 22) are provided between the magnet housing (14) and the valve housing (10), which are linked with the inflow socket (11) and with the interior of the magnet housing (14) via openings (24) arranged near the return yoke (27) in the magnet housing (14).
 8. A valve in accordance with claim 4, in which axial channels (21, 22) are provided between the magnet housing (14) and the valve housing (10), which are linked with the inflow socket (11) and with the interior of the magnet housing (14) via openings (24) arranged near the return yoke (27) in the magnet housing (14).
 9. A valve in accordance with claim 1, in which between the outflow socket (12) and that side of the return yoke (27) which faces the one flow socket, a non-return valve (45) is arranged in the valve housing (10), the valve seat (44) of which is designed on the valve housing (10) and the valve member (46) of which is pressed onto the valve seat (44) by a valve spring (47) which is supported on the outflow socket (12).
 10. A valve in accordance with claim 2, in which between the outflow socket (12) and that side of the return yoke (27) which faces the one flow socket, a non-return valve (45) is arranged in the valve housing (10), the valve seat (44) of which is designed on the valve housing (10) and the valve member (46) of which is pressed onto the valve seat (44) by a valve spring (47) which is supported on the outflow socket (12).
 11. A valve in accordance with claim 3, in which between the outflow socket (12) and that side of the return yoke (27) which faces the one flow socket, a non-return valve (45) is arranged in the valve housing (10), the valve seat (44) of which is designed on the valve housing (10) and the valve member (46) of which is pressed onto the valve seat (44) by a valve spring (47) which is supported on the outflow socket (12).
 12. A valve in accordance with claim 4, in which between the outflow socket (12) and that side of the return yoke (27) which faces the one flow socket, a non-return valve (45) is arranged in the valve housing (10), the valve seat (44) of which is designed on the valve housing (10) and the valve member (46) of which is pressed onto the valve seat (44) by a valve spring (47) which is supported on the outflow socket (12).
 13. A valve in accordance with claim 5, in which between the outflow socket (12) and that side of the return yoke (27) which faces the one flow socket, a non-return valve (45) is arranged in the valve housing (10), the valve seat (44) of which is designed on the valve housing (10) and the valve member (46) of which is pressed onto the valve seat (44) by a valve spring (47) which is supported on the outflow socket (12).
 14. A valve in accordance with claim 6, in which between the outflow socket (12) and that side of the return yoke (27) which faces the one flow socket, a non-return valve (45) is arranged in the valve housing (10), the valve seat (44) of which is designed on the valve housing (10) and the valve member (46) of which is pressed onto the valve seat (44) by a valve spring (47) which is supported on the outflow socket (12).
 15. A valve in accordance with claim 7, in which between the outflow socket (12) and that side of the return yoke (27) which faces the one flow socket, a non-return valve (45) is arranged in the valve housing (10), the valve seat (44) of which is designed on the valve housing (10) and the valve member (46) of which is pressed onto the valve seat (44) by a valve spring (47) which is supported on the outflow socket (12).
 16. A valve in accordance with claim 8, in which between the outflow socket (12) and that side of the return yoke (27) which faces the one flow socket, a non-return valve (45) is arranged in the valve housing (10), the valve seat (44) of which is designed on the valve housing (10) and the valve member (46) of which is pressed onto the valve seat (44) by a valve spring (47) which is supported on the outflow socket (12). 